Carbohydrates are ubiquitous. They densely carpet cell surfaces. They are the main component of the extracellular matrix that surrounds cells. They are involved in many aspects of cell-cell ­communication.

Glycans, a type of carbohydrate, are “the first thing a signaling molecule encounters when it contacts a cell,” says Robert J. Linhardt, a biochemist at Rensselaer Polytechnic Institute who studies carbohydrate structure and function. “They’re the first thing a virus encounters when it . . .